It gave the message that it was a patcher for sp2/sp3, if not it would mess up my system. I checked properties on my computer and it stated that it was now Service Pack 3. It required restart for changes, i initiated and now it BSODs where I mentioned above. I obviously must have f***ed up but i dont know where.
Message reads.

STOP: c000021a {Fatal System Error}
The WIndows Logon PRocess system process terminated unexpectedly with a status of 0x0000005 (0x00000000 0x00000000).
The system has been shut down.

STOP message sticky supplied little info for this particular status. What can i do short of re-installing os?